Recently, interest in a safety technique for an automobile has increased greatly. Thus, various preventive safety systems have been put to practical use mainly by an automobile related company and the like. Among these preventive safety systems, a system which uses Adaptive Cruise Control (hereinafter, referred to as “ACC”) or pre-crash control is widely known.
The ACC controls a vehicle traveling speed to a pre-set vehicle speed without an operation intervention by a driver or controls a distance between an own vehicle and a vehicle traveling ahead thereof to a predetermined distance (see, e.g., PTL 1).
Also, the pre-crash control is control to reduce impact of a collision by activating a brake or to reduce impact of a collision on an occupant by appropriately tightening a seat belt when it is not possible to avoid a collision with a target getting closer to an own vehicle from the front, side, or behind thereof (see, e.g., PTL 2).
Generally, control algorithm such as what has been described above is incorporated into a microcontroller or the like. A vehicle travel control system is realized by the following system configuration. That is, by calculating a control command such as acceleration, which is requested to the vehicle according to each kind of control algorithm, and by transmitting a command to a brake actuator, breaking of a vehicle is performed and by transmitting a command to a throttle actuator, driving of the vehicle is performed.
Here, a plurality of kinds of control algorithm is often incorporated into the microcontroller or the like. Thus, it is important to determine a control command from which control algorithm is employed to control a vehicle according to a condition.
For example, in a vehicle in which two kinds of control algorithm, which are the ACC and the pre-crash control, are mounted, when pre-crash control is started during the execution of the ACC, it is considered that a priority is given to a command of the pre-crash control having higher urgency.
However, when the above described condition is a case where a vehicle-to-vehicle distance suddenly becomes short due to sudden breaking of a preceding vehicle during preceding vehicle follow-up traveling control by the ACC, it can be assumed that acceleration is controlled in a deceleration direction by the ACC before determination to start the pre-crash control is made. In this case, when a control command is simply switched to a value calculated by the pre-crash control along with the determination to start the pre-crash control, it may be considered that breaking force is rather weakened depending on setting for calculating a control command in each kind of control algorithm.
As a method to solve such a problem, PTL 3 discloses a vehicle control system including: a distance detection unit configured to detect a distance between an own vehicle and a forward obstacle, which includes a preceding vehicle, in a predetermined range forward in a traveling direction of the own vehicle; a relative speed detection unit configured to detect a relative speed between the own vehicle and the obstacle; a first target acceleration calculation unit configured to calculate first target acceleration for keeping a set vehicle-to-vehicle distance based on a distance and a relative speed with the preceding vehicle in such a manner that follow-up traveling is performed with the set vehicle-to-vehicle distance away from the preceding vehicle traveling a traveling lane of the own vehicle; a second target acceleration calculation unit configured to calculate second target acceleration for decelerating the own vehicle when it is determined that the own vehicle may collides with the forward obstacle based on a distance and a relative speed with the forward obstacle; a third target acceleration calculation unit configured to calculate third target acceleration which is at least equal to or smaller than smaller one of the first and second target acceleration based on the first target acceleration and the second target acceleration when the second target acceleration is calculated by the second target acceleration calculation unit while the first target acceleration is calculated by the first target acceleration calculation unit; and a control unit configured to control a speed adjustment member including a brake system provided to the own vehicle in such a manner that acceleration of the own vehicle matches the third target acceleration when the third target acceleration is calculated by the third target acceleration calculation unit.
Also, other than these, a system to control a vehicle safely and comfortably similarly to a skilled driver by controlling a target longitudinal acceleration/deceleration control command according to a lateral jerk generated in response to a driver operation has been proposed (see, e.g., PTL 1 and PTL 2).